DOI measurement with monolithic scintillation crystals: A primary performance evaluation

We report a first assessment of image quality enhancement achieved by the implementation of depth of interaction detection with monolithic crystals. The method of interaction depth measurement is based on analogue computation of the standard deviation with an enhanced charge divider readout. This technique of depth of interaction detection was developed in order to provide fast and determination of this parameter at a reasonable increase of detector cost. The detector consists of an large-sized monolithic scintillator coupled to a position sensitive photomultiplier tube. A special design feature is the flat-topped pyramidal shape of the crystal. This reduces image compression near the edges of the scintillator. We studied the image enhancement qualitatively with a FDG filled hot spot phantom and quantitatively by displacing a single point source along a radial axis. An important uniformity improvement was observed for the reconstructed image of the hot spot phantom when depth of interaction correction was applied. A moderate improvement of the spatial resolution was observed when reconstructing the images of the point source with depth of interaction correction.